Rock Walls Research Articles

Recurrent Infections After Percutaneous Pinning of a Proximal Radius and Ulna Fracture.

Elbow fractures in the pediatric population are an exceedingly common injury, comprising 5% to 10% of all pediatric fractures, with supracondylar fractures being the most common of the subset. Radial neck fractures are less frequent, comprising only 1% of all pediatric fractures. We provide a case report of a 7-year-old girl with a left radial neck and proximal ulna fracture. A 7-year-old girl presented to the emergency department after falling off a rock wall the day before. Imaging showed a left proximal ulna and proximal radial neck fracture. The patient underwent percutaneous reduction and fixation, complicated by subsequent infection requiring surgical débridement. The patient then developed a recurrent infection 1 year later, requiring repeat irrigation and débridement. The patient has since made a full recovery, returned to activities of daily living, and regained a full range of motion. Radial neck fractures have a low incidence and have been frequently associated with poor outcomes. The main mechanism by which these fractures occur is due to falling on an outstretched arm. Percutaneous pinning is often recommended after unsuccessful attempts at closed reduction because open reduction is often complicated by postoperative stiffness. As with any procedure that involves breaking the skin, there is a risk of infection. However, there is unclear evidence regarding ideal perioperative management to prevent postoperative infection.

Study on Mechanism of Cumulative Directional Blasting of Brittle Karst Limestone in the Guizhou Province

The theoretical analysis, mechanical test, numerical simulations, and model tests are carried out on the Taoziya tunnel in Guizhou to investigate the influence law of cumulative blasting technology on directional rock breaking and fracture propagation of brittle limestone. The penetration effect of the triangular-shaped charge cover angle on the metal jet, the expansion law of the main explosion crack, and the influence of the limestone directional damage effect are explored. The results show that high-energy metal jet is formed when the initial velocity of the shaped charge cover is lower than the sound velocity of the shaped charge cover material. The values of B1 and B2 of the original rock are 22.1 and 248.76, respectively, demonstrating the mechanical properties of high strength, high brittleness, and easy fracture. The evaluation index is brittle limestone, and the directional precracking effect of shaped charge blasting technology is remarkable. When the angle of the shaped charge cover is 90°, a penetrating crack is almost consistent with the direction of the precrack generated after the explosion. Moreover, the width of the slit is approximately 2 cm. The borehole imager scans show that the rock wall in the hole is smooth and stable, the test results are consistent with the simulation results, and the angle of the shaped charge cover is 90°. The results have certain guiding significance for rock blasting technology, surrounding rock control technology, and similar directional fracturing engineering in the karst area of Guizhou province.

Temperature field of multi-barrier with gap layer in nuclear waste repository

A three-dimensional four-layer thermal conduction model including an air layer was developed to analyze temperature evolution in nuclear waste repository. Laplace-domain temperature solutions for each layer were obtained using finite Fourier transform and Laplace transform. The Laplace-domain solutions were transformed into time-domain semi-analytical solutions by numerical inversion. The surface temperature of central canister was obtained by superimposing the temperature increments of air and buffer layers on rock wall temperature caused by every canister in one disposal panel. The effects of the geometrical parameters, thermal parameters and nuclear waste parameters on surface temperature of canister were studied based on the obtained semi-analytical solution. The results indicate that the presence of air layer has little effect on temperature distribution in bentonite while its effect on temperature at surface of canister is significant. Thickness of air layer has a greater effect on temperature than that of its thermal conductivity. The burn-up value and cooling time also have significant influence on the temperature. Finally, the influences of repository’s geometric size on temperature in this model were analyzed.

Study of microscopic imbibition and formation plugging mechanism of the compact oil reservoir based on SEM and NMR analysis

Unconventional reservoirs, such as compact reservoirs, have been extensively developed. The Changqing Oilfield is currently the largest compact reservoir oilfield in China. An effective method for developing compact reservoirs using hydraulic fracturing for reservoir modification is required. Some wells exhibited small production increases after fracturing, and some showed reductions in production. The impact mechanism of the fracturing fluid on the reservoir remains unclear. We used nuclear magnetic resonance (NMR) analysis and scanning electron microscopy (SEM) to investigate the utilization of a nano-micropore fluid and the surface morphology of the matrix during imbibition after fracturing. The results indicated polymer adhesion on the rock wall after the imbibition. The capillary force and the soaking pressure were the dominant driving forces during the imbibition. The capillary force was dominant in the small pores, and the soaking pressure had a larger influence on the fluid utilization of the large pores. The medium pores exhibited more significant solid phase damage, and the fluid utilization degree was relatively low. This study clarifies the impact mechanism of the fracturing fluid on the reservoir and the imbibition mechanism of slickwater. The results provide theoretical support and a scientific basis for optimizing fracturing, flowback methods, and post-fracturing stimulation in compact reservoirs.

PEAK DIFFERENTIAL TIDAL PRESSURES FOR ROCK WALL RECLAMATION AREAS

Unexpected differential tidal pressures occurred during construction of a 62 Ha reclamation area at Townsville Port. The reduction in tidal flows through a new rock wall structure was in conjunction with installation of a geotextile membrane. Tidal pressures began to displace the geotextile and cover rock. This paper discusses tide data collected during various stages of construction and how it was used for estimating progressive tide differentials. These estimates assisted with forecasting potential issues.

Malacofauna of Bolków castle (Lower Silesia, SW Poland) – trends and perspectives

Bolków castle is located in the Lower Silesian voivodeship near the Kaczawskie Mountains. Malacological studies were carried out in 2006, 2010 and 2021. In 2006, specimens were collected only by hand, but in 2010 and 2021 samples were also made by litter sieving and from material taken from rock shelves and walls. Overall, 35 species were found, but the numbers declined over time: 28 species in 2006, 26 in 2010 and 20 in 2021. Two species recorded before our studies were not found again. Abundance declined greatly between 2010 and 2021. Over this period, open-country species declined the most, and shade-loving species increased as a proportion of the whole. In particular, the open-country Pupilla muscorum, eudominant in 2010, was absent in 2021, while the tolerant Alinda biplicata increased greatly over the same period. While more widespread environmental or climatic change may be involved, the castle has been subject to increased human pressure and a renovation programme in 2015. Castle faunas, here and elsewhere, are not only refugia for locally or nationally uncommon species, but provide a basis for regular monitoring of faunal change. Other castles in the region, most especially those at Stary Książ and Książ have similar faunas, and can be used in the same way.

Design and numerical analysis of Cross-Laminated bamboo (CLB) buildings with different rocking wall configurations

Engineering bamboo attracts increasing attention due to its renewable, low-carbon properties as well as the high strength-to-weight ratio. This paper proposed a displacement-based design (DBD) method for cross-laminated bamboo (CLB) rocking wall buildings based on experimental tests. The DBD was to control the story drift limitation considering the collapse prevention (CP) hazards level. The DBD accounted for the detailed design of prestressed tendons (PT) and conventional friction dampers (CFD). Segmented and monolithic rocking wall configurations were designed based on DBD and applied in the building. The simplified numerical models (SNM) for those two rocking walls were established in ABAQUS using cartesian connectors. Then two three-story CLB building models, i.e., X-LamBR1 with segmented rocking wall and X-LamBR2 with monolithic rocking wall were developed. Modal analysis and time history analysis were conducted with these two models. Smaller inter-story displacement, acceleration, and shear force were observed in X-LamBR2. Simulation results indicated that building with a monolithic rocking wall configuration performed better under earthquake excitation.

Numerical Simulation Verification of the Application of Inorganic Thermal Insulation Materials to the Surrounding Rock of Roadways

Insulation materials provide a new solution for heat dissipation control in high-temperature mine enclosures. In this paper, ANSYS Fluent was selected to conduct a numerical simulation study on the heat transfer after inorganic insulation materials were laid on the surface of the mine tunnel surrounding rock. The results show that the influence of the tunnel wind flow on the temperature of the surrounding rock is related to the support material laid, and the temperature of the surrounding rock wall after laying inorganic insulation material is about 4°C lower than that of ordinary concrete support. The temperature difference of the surrounding rock wall at the entrance of the tunnel is about 4.6°C, and that of the surrounding rock wall at the exit is about 2.8°C. The comparative analysis verifies that the insulation material positively affects the heat dissipation control of the high-temperature shaft and the surrounding rock of the roadway.

Experimental Investigation of Precast Rocking Walls Incorporating Tension-Compression and Shear Steel Energy Dissipaters

To fully utilize the potential of earthquake-resistance capacity in rocking wall systems and improve repairability after earthquakes, a precast rocking wall structure is developed with the installation of multiple steel energy dissipaters, i.e., tension–compression and shear steel energy dissipaters. Quasistatic tests were carried out on three specimens to evaluate the seismic performance of the proposed system. A simulation investigation based on OpenSees was conducted to study the effects of the initial stress of strands and the main design parameters. The results indicated that the steel energy dissipaters suffer visible plastic deformation and exhibit excellent energy dissipation capacity. The proposed rocking wall structure presents excellent seismic behavior, satisfactory self-centering capacity, and repairability of the recovering function after an earthquake by replacing only the damaged energy dissipaters. Furthermore, the proposed system provides a new way to achieve the hierarchical energy dissipation mechanism of a structure.

An XFEM-based hydro-mechanical model to consider the non-Darcy flow in complex fracture networks

Geotechnical instability and failure are closely related to the hydro-mechanical coupled behavior of fractured rocks, and the existing studies often regard the fracture seepage as linear Darcy flow. Due to the neglect of non-Darcy effect caused by rough rock wall and high flow velocity, the estimated rock deformation and seepage flow can lead to incorrect assessment of geotechnical risks. Hence, this study proposed an efficient and robust hydro-mechanical (HM) coupled model to consider non-Darcy flow in complex fracture networks. The fractured rock mass's mechanical response, including the fracture surface's frictional contact, was calculated using the XFEM solver, and the widely used Forchheimer's law was adopted to describe the non-Darcy flow along the fractures. The fracture segments cut by mechanical element edges are considered one-dimensional flow elements, and the Newton-Raphson iteration method is adopted to solve the Forchheimer equation directly. To consider the influence of fracture deformation on the conductivity of fractures, the Barton-Bandis model was adopted to determine the hydraulic aperture of the fractures when the fracture was closed. Subsequently, a staggering Newton-Raphson method can be developed to decouple the fracture deformation and fluid flow process. Experimental results were adopted to validate the accuracy of the numerical model, and several numerical cases were used to illustrate the efficiency and robustness of the proposed model. The effects of inlet pressure, confining stress, and non-Darcy effect on the HM-coupled behavior of fractured rock were investigated. Numerical results suggested that the distribution of fluid pressure and failure process of rock mass based on Darcy assumption could be dramatically changed after considering the nonlinear seepage behavior.

Development and seismic performance of precast rocking walls with multiple steel energy dissipaters

To enhance the repairability of lateral force resisting systems after earthquakes, a novel precast rocking wall with multiple steel energy dissipaters (PRW-MED) was devised, and a hierarchical energy dissipation (HED) mechanism was proposed based on this structure. Three quasistatic tests were conducted on the rocking wall specimens to evaluate the seismic performance of the PRW-MED. Simulations of the experiment were carried out in OpenSees software, and the influences of several parameters on the performance of the PRW-MED were investigated. The results indicated that the structure possessed excellent self-centering and deformation capabilities; the multiple dissipaters contributed sufficient energy dissipation capacity to the structure, and the parameters of the steel panel dampers (SPDs) exhibited significant effects on the seismic performance of the structure. Meanwhile, the experiment proved that the application of multi dissipaters led to the proposed HED mechanism. The parametric analysis demonstrated that the design parameters including initial stress of strands, thickness of SPD, and width of SPD etc. contributed significantly to the seismic performance of PRW-MED.

Suitability of terrestrial archival imagery for SfM-MVS based surface reconstruction of steep rock walls for the detection of rockfalls

Suitability of terrestrial archival imagery for SfM-MVS based surface reconstruction of steep rock walls for the detection of rockfalls

Assessing the rock failure return period on an unstable Alpine rock wall based on volume-frequency relationships: The Brenva Spur (3916 m a.s.l., Aosta Valley, Italy)

Defining the relationship between volume and return period is critical when estimating the risk of rockfalls and/or rock avalanche, especially during continued global warming at high altitudes that threatens rock wall stability. Characterizing the volume-frequency relationship based on historical datasets is, however, limited by observation and quantification biases, which have not received enough attention. Here, to monitor recent activities for the Brenva Spur (Mont-Blanc massif, Italy) that is also a rock avalanche scar and estimate the return period of future rock failures based on the volume-frequency relationship (and the corresponding uncertainty), a structure-from-motion photogrammetric survey was conducted from 2017 to 2021. 39 rockfall sources with volumes ranging from 11 to 13,250 m3 were identified within the scar. The total failure volume is 22,438 m3, with an associated erosion rate of 15.5 mm/year, indicating very active morphodynamics possibly linked to the permafrost evolution in the spur. The volumes were characterized by a negative power-law that fits significant two events in 2016 (3.4 × 104 m3) and one in 1997 (2.0 × 106 m3) remarkably well, and the randomness of the fit was evaluated by a Monte Carlo approach. 7 potential failure scenarios ranging from 3.1 × 104 m3 (S1) to 4.8 × 106 m3 (S7) were defined according to a structural analysis and the sloping local base level concept. Their extrapolated return periods derived by the power-law fit indicate a longer return period for the maximum failure scenario than for the smaller scenarios. S1 has a 50% chance of occurring every 3 years, while S7 has a 50% chance of occurring every 31 years. Though the median return period of S7 is 31 years, the 95% and 68.2% confidence intervals range from 8 to 399 years and 14 to 93 years, respectively, which reflects a high level of uncertainty but is realistic when considering global warming, progressive rock failure, etc. In addition to characterizing recent rock failure activities in high mountains, this study offers a preliminary examination of the return periods of some extreme scenarios and provides primary data for risk management in mountainous areas that are very sensitive to global warming.

Estimating the Evolution of a Post-Little Ice Age Deglaciated Alpine Valley through the DEM of Difference (DoD)

Since the end of the Little Ice Age (LIA, ~1830), the accelerated glaciers’ shrinkage along mid-latitude high mountain areas promoted a quick readjustment of geomorphological processes with the onset of the paraglacial dynamic, making proglacial areas among the most sensitive Earth’s landscapes to ongoing climate change. A potentially useful remote-sensing method for investigating such dynamic areas is the DEM (Digital Elevation Model) of Difference (DoD) technique, which quantifies volumetric changes in a territory between successive topographic surveys. After a detailed geomorphological analysis and comparison with historical maps of the Martello Valley (central Italian Alps), we applied the DoD for reconstructing post-LIA deglaciation dynamics and reported on the surface effects of freshly-onset paraglacial processes. The head of the valley is still glacierized, with three main ice bodies resulting from the huge reduction of a single glacier present at the apogee of the LIA. Aftermath: the glaciers lose 60% of their initial surface area, largely modifying local landforms and expanding the surface of the proglacial areas. The DoD analysis of the 2006–2015 timeframe (based on registered DEM derived from LiDAR—Light Detection and Ranging—data) highlights deep surface elevation changes ranging from +38 ± 4.01 m along the foot of rock walls, where gravitative processes increased their intensity, to −47 ± 4.01 m where the melting of buried ice caused collapses of the proglacial surface. This approach permits estimating the volume of sediments mobilized and reworked by paraglacial processes. Here, in less than 10 years, −23,675 ± 1165 m3 of sediment were removed along the proglacial area and transported down valley, highlighting the dynamicity of proglacial areas.

Effect of serviceability limit state and over-strength mechanism on seismic performance of self-centring low damage structures with friction connections

Low damage design is an alternative to conventional seismic design, where earthquake-induced damage in the building is controlled and minimised. The most common approach to implement this concept is to design the structural system in a way that damage occurs in a series of specified components. This makes the designer able to predict the performance of the building under earthquakes by deliberately designing these components weaker than the other parts of the structure. These components can be replaced, repaired, or even designed to remain functional after earthquakes. Therefore, the performance of such components (e.g. weak links) is critical for evaluting the performance of the building as a whole.The New Zealand standard defines two extra limit states in addition to the design level earthquake (Ultimate Limit State (ULS)). First is the Serviceability Limit State (SLS), where the system is expected to remain linear and elastic, and the second is the collapse limit state (also known as MCE limit state), where damage is accepted, but the building should not collapse. For a low damage system, the weak links should be designed to remain linear and elastic under SLS actions. Also, they should have adequate reserve capacity to not completely fail under MCE actions. The latter is also called the over-strength mechanism (or the upper bound design level) for designing the low damage components. This study investigates the effect of the over-strength and serviceability limit state on the overall seismic performance of low damage systems. Two types of generic structural responses are considered for the study, self-centring braced frames and self-centring rocking wall systems. Numerical models for both concepts are developed and subjected to nonlinear dynamic time-history analysis with different intensities up to large, rare events (MCE). The results showed that braced frames' appropriate over-strength capacity is relatively smaller than rocking walls. The findings of this study help designers and engineers to perform more efficient and optimised designs for low damage systems. Also, this research helps them to have a better understating of the performance of such systems under large, rare earthquake events.

Moon Diver: Exploring a pit's exposed strata to understand lunar volcanism

Natural pits on the Moon expose deep cross-sections of the lunar maria, enabling direct investigation of the Moon's volcanic history and providing potential access to subsurface lava tubes. The Moon Diver mission concept seeks to explore the Mare Tranquillitatis pit, which exposes the largest wall of bedrock of the mare pits (∼65 m). The concept is enabled by two innovative capabilities: pinpoint landing near the pit and robotic access to its near-vertical wall with an instrument package to examine the elemental chemistry, mineralogy, and morphology of these bedrock layers. Pinpoint landing uses closed-loop guidance with terrain-relative navigation (TRN), which was advanced by Perseverance landing on Mars, to deliver the lander within a 100-m ellipse. The Axel robotic explorer, which remains tethered to the lander, would egress onto the lunar surface and traverse the relatively flat terrain to the pit's funnel entrance. The lander, which is the data link to Earth, also serves as an anchor and provides power and communication to the rover through its tether. The rover is a novel two-wheeled platform with a trailing boom and a spool that pays out the tether as the rover traverses toward the pit. The 300-m long tether is well margined for the rover to scale the pit wall. The rover carries a surface preparation tool and three additional instrument types: (a) three high-resolution cameras for acquiring context images of the near and far walls with the near-wall pair in a stereoscopic configuration, (b) an alpha-particle-X-ray spectrometer (APXS) for elemental composition, and (c) a multi-spectral microscopic imager (MMI) that uses controlled lighting for mineralogy. The surface-preparation tool removes dust and patina from the rock wall by grinding a small area. This tool, the MMI, and the APXS would be deployed from an instrument bay inside the wheel wells. The rover would independently point each instrument at the same target on the wall with millimeter repeatability. Landing shortly after sunrise, the surface mission timeline is just shy of a lunar daytime (14 Earth days). Beyond the primary mission, the rover would be capable of descending from the overhang and peering into the void that may open to a large cave or lava tube. Lunar pits provide an exciting new target for exploration using innovative robotic capabilities that have been tested with integrated science instruments at multiple terrestrial analogue sites including a pit with basaltic layers in Arizona.

Seismic Performance of an Earthquake Resilient Self-Centering Precast Reinforced Concrete Rocking Wall with External SMA Rods

ABSTRACT This research aims to propose an alternative way to provide a recentering force to a precast unbonded post-tensioned reinforced concrete rocking wall (RW) using shape memory alloy (SMA) bars. The physical and mechanical properties, such as fatigue, corrosion resistance, and large damping capacity, qualify the SMA to be at the forefront of materials used in structural engineering applications. In this study, the SMA bars replace the post-tensioned tendons to minimize the permanent deformation resulting from the system’s exposure to the lateral loading coming from the seismic events. The SMA bars are attached externally to the wall and fixed with the base to facilitate the installation process and reduce the repairing time if a failure occurs under unexpected events. The proposed system shows that the SMA rods can play the same role as the PT tendons to minimize the residual displacement while also providing an acceptable level of energy dissipation to the system.

Morphological and molecular data on a new species of Polygala (Polygalaceae) from Turkey

Polygala fadimeana Dönmez and Çeçen is here described as a new species from the inner part of the Taurus mountain range in Turkey based on morphological data and its phylogenetic position is discussed based on molecular data. This new species is confined to limestone rock walls and is morphologically distinguished from P. kurdica and P. peshmenii by smaller plant size, nearly glabrous leaves, enrolled inner sepals, white colour crest, and other minor diagnostic features. However, a multi‐locus chloroplast phylogeny (trnL‐F and rbcL) including accessions of the new species and related taxa of Turkish Polygala revealed a close relationship to P. pruinosa and P. supina. The taxonomic relationship among the new species and P. kurdica, a poorly known species from Zagros Mountain range, and other closely related species such as P. pruinosa, P. peshmenii and P. supina are discussed. The new species is assessed as critically endangered (CR) based on current knowledge and the distribution of the new species and related taxa is mapped.

Hyperepilithics—An overlooked life form of vascular plants on tropical vertical rock walls

AbstractVascular epiphytes are a characteristic life form in many tropical regions and often occur growing on bare rocks. South America has the highest diversity. Here, we describe a neglected life form: hyperepilithics adapted and restricted to growing on vertical (inclination above 70°) and bare rock walls without having roots intruding the substrate. Hyperepilithics are in particular present on Brazilian inselbergs and dominated by highly specialized Bromeliaceae, mainly of the genera Stigmatodon, Tillandsia and Alcantarea, whereas Orchidaceae surprisingly has a low representation. An overview of this habitat, the life form hyperepilithics and a comparison with similar paleotropical habitats (mainly inselbergs in Western/Eastern Africa and India) are provided. Attention is drawn to hyperepilithics as a most promising and not yet exploited source for a sustainable urban ‘vertical gardening’, for example in tropical megacities.

The coupled cooling effect of ventilation and spray in the deep-buried high-temperature tunnel

The utilization of ventilation and spray cooling technology is becoming increasingly popular in high-temperature workplaces due to its convenience and environmental friendliness. To investigate the coupled cooling effect of ventilation and spray in a construction tunnel, we established a droplet evaporation model under convective heat transfer conditions by combining the convective heat transfer theory and the droplet heat and mass transfer model. Based on this model, the study focused on the energy change of droplet evaporation in a moving medium by using numerical simulation in the context of a railroad construction tunnel. The material of the droplets used in the study was water. According to the simulation and field measurement results, it was obtained that, firstly, increased air volume of the tunnel and reduced airflow temperature could make the convective heat exchange stronger between the airflow and the wall. Secondly, the particle size of droplets formed by spraying was mainly 30–40 μm in the tunnel. A part of the droplets was evaporated in the high-temperature environment, and another part was trapped by the rock wall and ground. Third, adopting the coupled cooling method of ventilation and spray, the temperature and humidity fields in the tunnel changed significantly, and a low-temperature and high-humidity zone appeared near the nozzle. At the same time, the evaporation rate of droplets increased, the heat index of the workplace decreased, and the cooling effect was effective. Therefore, the coupled cooling method of ventilation and spray can effectively improve the thermal environment in high-temperature construction tunnels and enhance the thermal comfort of personnel. This study serves as a reference for the parameters and cooling effect of ventilation and spray cooling systems in construction sites.